This invention relates to a disposable lap blank capable of being custom cut to fit the prescribed contour of a lens blank thus allowing where necessary for off-axis polishing of the lens blank through the intermediary of the custom fit lap wherein the improvement in such lap includes a means provided in the disposable lap for receiving a holder capable of mounting it for cutting to a surfacing machine and subsequently to a finishing or polishing machine for polishing of the lens blank for which it was custom cut.
In U.S. Pat. No. 4,989,316 entitled METHOD AND APPARATUS FOR MAKING PRESCRIPTION EYEGLASS LENSES, issued to Logan, et al. on Feb. 5, 1991, commonly assigned herewith, and in the aforesaid copending U.S. patent application Ser. No. 07/604,052, entitled SINGLE BLOCK MOUNTING SYSTEM FOR SURFACING AND EDGING OF A LENS BLANK AND METHOD THEREFOR, a disposable lap blank is disclosed wherein the lap is adapted to be held in driving rotation in a surfacing machine which shapes it by cutting in order create thereon an inverse profile of the surface cut into the lens. Additionally, it is therein disclosed to utilize the same lap and associated holding means to secure the custom cut lap blank on a finishing machine wherein the cut lens surface undergoes polishing. Hitherto the holding means used to generically mount the lap blank in its initial uncut state to the surfacing machine and subsequently after cutting to a polishing machine, was carried by the blank as an integral part thereof. This involved the use of a steel backing plate which during the manufacturing process of the stock laps first had to be mounted to the rear face of the lap blank on a raised portion thereof to allow gripping of it by the respective surfacing and finishing machines. Fabricating the stock lap blank piece with the metal plate was very labor intensive. First, it required the worker to carefully align the raised portion of the lap blank with the plate. An adhesive applied to the plate caused it to be bonded with the lap at the angle it dried at regardless of whether it was perfectly aligned with the underlying portion. Any such misalignment would adversely affect the outcome of the lens being made in that the plate and the underlying raised portion might be gripped at different angular orientations by the different means used for holding the blank in each of the surfacing and finishing machines. This is especially critical in the situation where laps having a very high cylinder component to them are so misaligned with the backing plate such that even the slightest twist or axis shift can be critical to the polishing result sought to be achieved. Additionally, in these previously known lap blanks it was required during the manufacturing process to affix a small magnetic piece at a designated location on the lap for the purpose of indicating to the surfacing machine that it was presently cutting a lap blank rather than a lens blank and that the inverse of the lens configuration was to be cut instead into the lap blank thereby customizing it to fit the lens configuration. Such individual fitting of magnetic pieces to each of the laps added still another labor intensive step involved in their manufacture. This practice was further made cost ineffective by the magnetic strip having to be thrown away with the disposable blank after use.
Accordingly, it is an object of the present invention to provide a disposable lap blank wherein the improvement comprises a separate holder having a means which releasably, yet securably engages the lap blank to hold it in such orientation while the lap surface is either being cut in a surfacing machine or while the lap is being used to polish the cut lens surface. In keeping with the foregoing object, a more specific object of the invention is to provide in a lens making system, a lap blank and associated holder assembly wherein the holder is adapted to be received and held generically in driving engagement within the lens surfacing machine and within the polishing machine thus avoiding the hitherto problems associated with fabricating the mounting parts on the disposable lap.
A still further object of the present invention is to provide a disposable lap and a reusable holder assembly of the aforementioned type wherein the holder is readily secured to the disposable lap blank in a given orientation through the intermediary of coengaged pieces adapted to releasably yet securably hold the two members to one another.
Yet still a further object of the present invention is to provide a lap blank holder of the aforementioned type wherein the holder is configured such that it is readily held in a given orientation by the user allowing it to be inserted into the lap blank without significant aligning checks being made.
Further objects and advantages of the present invention will become apparent from the following Disclosure and the appended claims.